Actuator control system

ABSTRACT

A system comprising an actuator and a controller configured to drive the actuator with a pulse width modulated (PWM) signal. The controller is configured to limit a duty cycle of the PWM signal in response to a current supplied by the PWM signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date ofprovisional application Ser. No. 61/586,549 filed on Jan. 13, 2012,which is incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments relate to actuator control systems and, in particular, toactuator control systems for engines.

BACKGROUND

Electric actuators can be used to actuate components of an engine of avehicle. Electric motors can be used to actuate throttles, steeringcomponents, various mechanical linkages, or the like. Electrical systemsusing such components can have varying specifications, such as powersupply voltages. To accommodate such different systems differentelectrical actuators designed for the different supply voltages can beused, increasing production and maintenance costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an actuator control system according to anembodiment.

FIG. 2 is a block diagram of an actuator control system according toanother embodiment.

FIG. 3 is a block diagram of duty cycle limiting in an actuator controlsystem according to another embodiment.

FIG. 4 is a block diagram of an actuator control system according toanother embodiment.

FIG. 5 is a block diagram of an engine system with an actuator controlsystem according to another embodiment.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, and any alterations and furthermodifications in the illustrated embodiments, and any furtherapplications of the principles of the invention as illustrated thereinas would normally occur to one skilled in the art to which the inventionrelates are contemplated herein.

FIG. 1 is a block diagram of an actuator control system according to anembodiment. In this embodiment, the actuator control system 10 includesa controller 12 and an actuator 14. The controller 12 is configured todrive the actuator 14 with a pulse width modulated (PWM) signal 16. Inparticular, the controller can be configured to limit a duty cycle ofthe PWM signal

The controller 12 can be any variety of controller. For example, thecontroller 12 can be a dedicated controller solely for controlling theactuator. In another example, the controller 12 can be part of a largercontrol system, such as an engine control system. The controller 12 canbe implemented in a variety of ways. For example, the controller 12 caninclude a general purpose processor, a programmable logic device, anapplication specific integrated circuit, discrete components, a digitalsignal processor, a combination of such devices, or the like. Moreover,the controller 12 can, but need not be a single device. That is, thecontroller 12 can include multiple distributed components.

The actuator 14 can be any actuator that can be driven by a PWM signal.For example, the actuator 14 can be a brushless direct current (BLDC)motor. In another example, the actuator 14 can be a solenoid. In anotherexample, the actuator 14 can be a linear motor. In an embodiment, anydevice that is controlled by applying a current to generate a magneticfield that interacts with another magnetic field can be used as theactuator 14.

FIG. 2 is a block diagram of an actuator control system according toanother embodiment. In this embodiment, the actuator control system 30includes a controller 32 coupled to an actuator 50. The controller 32includes a processor 34, a driver 36, and a current sensor 38.

The driver 36 is configured to drive the actuator 50 using a PWM signal48. The driver 48 is configured to generate the PWM signal 48 inresponse to a PWM signal 40 from the processor 34. For example, thedriver 36 can include multiple transistors that switch in response tothe PWM signal 40. Thus, the PWM signal 48 can be a signal that providesthe power to actuate the actuator 50.

Using a BLDC motor as an example, the PWM signal 48 can be multiplesignals for multiple phases associated with the BLDC motor. That is, thePWM signal 48 can include multiple individual PWM signals, each phaseddifferently. Coils of the BLDC motor are powered by the PWM signal 48.That is, current supplied to the actuator 50 is provided by the driver36. Accordingly, the current sensor 38 can be configured to sense anamount of current supplied by the driver 36 through connection 42.

The current sensor 38 can be any variety of sensor. For example, thecurrent sensor 38 can include one or more series resistors, amplifiers,or the like. In another example, the current sensor 38 can be a virtualcurrent sensor that uses other measured values to estimate a current.Any parameter related to a current supplied by the driver can be sensedand used to generate the current signal 46. The current sensed can, butneed not be the exact current that is supplied to the actuator 50. Thatis, the current sensed can be a current that represents the currentsupplied to the actuator 50.

The processor 34 is configured to receive the current signal 46 from thecurrent sensor 38. The processor 34 can be configured to limit a dutycycle of the PWM signal 40, and hence, a duty cycle of the PWM signal 48in response to the sensed current 46. In an embodiment, a particularcurrent over a threshold can damage or deteriorate components of theactuator 50. By limiting the duty cycle, an effective current suppliedto the actuator 50 can be limited to reduce a change of damage,deterioration, or the like.

Similar to the PWM signal 48, the current sensed by current sensor 38can be a single current signal, multiple current signals each associatedwith a different individual PWM signal of the PWM signal 48, or thelike. Furthermore, although one or more PWM signals have been describedas being generated by the controller 32, received by the actuator 50, orthe like, other signal, connections, power supplies, or the like can beconnected to the actuator. For example, the actuator 50 can receive apower supply for a sensor such as a speed sensor, a position sensor, orthe like. The actuator 50 can provide sensed signals to the controller32. Any signal, connection, or the like, beyond the PWM signal 48 can becoupled between the controller 32 and the actuator 50.

Moreover, the PWM signal 40 can, but need not be identical to the PWMsignal 48 supplied to the actuator 50. For example, a single PWM signal40 can be supplied to the driver 36 with a particular duty cycle. Thedriver 36 can be configured to generate multiple individual PWM signalsof the PWM signal 48, such as different phases for driving the actuator.Each such signal can have the duty cycle substantially similar to theduty cycle of the PWM signal 40 from the processor 34.

FIG. 3 is a block diagram of duty cycle limiting in an actuator controlsystem according to another embodiment. In an embodiment, this diagramcan represent logic within a controller described herein. A requestedduty cycle 70 can be generated by particular sub-system of thecontroller associated with the actuator. For example, a particular stateof an inlet of a turbine can be desired for current engine operatingconditions. The requested duty cycle 70 can be generated to attempt toachieve the desired state.

However, with current operating conditions, the requested duty cycle 70may cause damage, deterioration, or the like to an actuator.Accordingly, the requested duty cycle 70 can be limited by limiter 72 togenerate a limited duty cycle 74. In particular, the requested dutycycle 70 can be limited by duty cycle limit 76.

In an embodiment, the requested duty cycle 70 can have a positive ornegative polarity. Accordingly, the limiter 72 can be configured tolimit a magnitude of the duty cycle in response to the duty cycle limit76. However, in another embodiment, the duty cycle limit 76 can includepositive and negative maximums, high and low limits, excluded ranges, orthe like. Furthermore, in an embodiment, a single polarity duty cyclesignal can be used. That is, the limits imposed by the limiter 72 can beset as desired in response to the duty cycle limit 76.

In an embodiment, a duty cycle of the PWM signal can be limited inresponse to a current supplied by the PWM signal, a requested dutycycle, and a current limit. For example, the requested duty cycle 70 canbe limited in response to the present duty cycle 74, a current limit 80,and a measured current 84.

The measured current 84 can represent the current signal 46 describedabove. That is, the measured current 84 can represent a current used todrive an actuator. The product of the current limit 80 and the dutycycle 74 is divided by the measured current 84 to generate a duty cyclelimit 76. For example, equation 1 represents the duty cycle limitcalculation.

$\begin{matrix}{{DutyCycleLimit} = \frac{{CurrentLimit} \times {DutyCycle}}{MeasuredCurrent}} & (1)\end{matrix}$

That is, the current limit 80 is multiplied by the duty cycle 74. In anembodiment, the current limit 80 can be multiplied by a magnitude of theduty cycle 74 as represented by magnitude operator 78. The product isdivided by the measured current 84. In other words, a current limit canbe converted into a duty cycle limit. In addition, a relationshipbetween a present duty cycle and a sensed current can be used to converta current limit into a duty cycle limit.

In an embodiment, the result can be limited by limiter 86. For example,the duty cycle limit can be limited to between about 10% and about 100%.In some circumstances, a division by a low sensed current, a low dutycycle, or the like could result in a lower duty cycle limit 76.Accordingly, a lower limit on the duty cycle limit can be established.In other circumstances, a particular duty cycle could substantiallyavoid damage and/or deterioration regardless of temperature, powersupply voltages, or other operation conditions. Such a duty cycle couldbe used for the lower limit. Thus, even though the various parametersand measurements may result in a lower calculated duty cycle limit, ahigher duty cycle limit can be used. Although particular examples havebeen given, other threshold limits can be used to limit the duty cyclelimit.

In an embodiment, the controller can be configured to substantiallycontinuously raise a limit on the duty cycle of the PWM signal. Forexample, a resistance of an actuator can decrease in certain conditions.For example, if a temperature of the actuator is relatively low, theresistance can also be relatively low. For a given duty cycle, if theresistance is lower, the current supplied can be greater and potentiallymeet the current limit 80.

However, as a system including the actuator operates, the temperaturecan increase, increasing the resistance of the actuator. Thus, for agiven duty cycle, the current supplied and hence, the measured current84 decreases. As the measured current 84 decreases, the duty cycle 76increases, allowing the limited duty cycle 74 to correspondinglyincrease if it was limited by the limiter 72. Accordingly, the dutycycle limit can have an initial lower lever and, as temperatureincreases during operation, the duty cycle limit can substantiallycontinuously increase.

Although the duty cycle 74 is illustrated as a generated signal, theduty cycle 74 used to multiply with the current limit 80 in forming theduty cycle limit 76 can be a measured signal. For example, similar tothe current sensor described above, a duty cycle sensor can generate asignal representative of the duty cycle used to drive the actuator. Thismeasured duty cycle can be used in the calculation of the duty cyclelimit 76.

FIG. 4 is a block diagram of an actuator control system according toanother embodiment. In this embodiment, the actuator control system 100includes a power supply 102, a controller 104, and an actuator 108. Thecontroller 104 is coupled to the actuator 108 and is configured toprovide a PWM signal 110 as described above. The controller 104 isconfigured to receive a voltage 106 from the power supply 102.

In different embodiments, the voltage 106 from the power supply 102 canbe different. For example, in one embodiment, the voltage 106 can beabout 12V. In another embodiment, the voltage can be about 24V.

Different actuators 108 can be designed to accommodate different voltagesupplies. For example, one actuator can be designed to operate with a12V PWM signal while another actuator can be designed to operate with a24V PWM signal. Such actuators 108 can be different models which, whendesigning a system for multiple power supply voltages, can increaseexpenses due to parts tracking, inventory, or the like.

However, in an embodiment, the controller 104 can be configured to drivethe actuator 108 even if the power supply 102 supplies differentvoltages 106. That is, a single actuator 108 with a given voltage ratingcan be used even though the power supply voltage 106 can result in a PWMsignal 110 that exceeds the rated voltage. In particular, the controller104 can be configured to limit a duty cycle of the PWM signal 110 inresponse to the power supply voltage 106.

In an embodiment a duty cycle limit can be dependent on the voltage 106.For example, the controller 104 can be configured to substantially limita maximum of the duty cycle of the PWM signal 110 to a ratio of a basevoltage to the voltage 106 of the power supply. Using 12V and 24V asexamples, the base voltage can be 12V. If the voltage 106 is 24V, theduty cycle can be limited to about 12V:24V, or about 50%.

Accordingly, an actuator with a particular rated voltage, such as 12V,can be used in a system with a higher power supply voltage 106 of 24V.In an embodiment, the base voltage can be the rated voltage; however, inother embodiments, the base voltage can be smaller or larger, but stillless than the power supply voltage 106 in particular applications.Although particular examples have been given, namely 12V and 24V, thevoltages of the components, power supplies, or the like can be selectedas desired.

FIG. 5 is a block diagram of an engine system with an actuator controlsystem according to another embodiment. In this embodiment, the enginesystem 130 includes an engine control module (ECM) 132. The ECM 132 canbe configured to control various operations of the engine system 130. Inparticular, the ECM 132 can be configured to control an actuatorassociated with a turbine 138.

For example, the ECM 132 can be configured to drive a brushless directcurrent (BLDC) motor 134. The ECM 132 can be configured to generate aPWM signal 136 to drive the BLDC motor 134.

The BLDC motor 134 can be coupled to the turbine 138. For example, theturbine 138 can be a variable geometry turbine. A linkage 140 canconnect the BLDC motor 134 to the turbine 138 such that the BLDC motor134 can change the geometry of the particular turbine 138. In anembodiment, the BLDC motor 134 can be mounted on or otherwise integratedwith the turbine 138. The ECM 132 can be configured to actuate the BLDCmotor 134 as described above. In particular, the ECM 132 can be coupledto the BLDC motor 134 through a cable harness and configured to drivethe actuator through the cable harness.

Although a single BLDC motor 134 has been illustrated, any number ofactuators and corresponding parts of the turbine 138 can be controlledas described above. Moreover, any number of BLDC motors 134, otheractuators, or the like can be controlled as described above.

Although a turbine 138 has been used as an example, in an embodiment,other components of the engine system 130 and components of a vehiclecontaining the engine system 130 can be actuated and controlled by theECM 132 or other controller as described above. For example, throttles,exhaust gas recirculation valves, wastegates, electric power steeringsystems, or the like can be driven by the ECM 132 or similar controller.

Furthermore, although only an ECM 132, BLDC motor 134, and a turbine 138have been illustrated as part of the engine system 130, other componentscan be present, but were omitted for ease of illustration. For example,engine blocks, compressors, exhaust systems, aftertreatment systems, orthe like can be part of the engine system 130.

An embodiment includes a computer-readable medium storingcomputer-readable code that when executed on a computer, causes thecomputer to perform the various techniques described above.

Although particular sequences of operations have been described above,in other embodiments, the sequences can occur as desired.

Although particular embodiments have been described above, the scope ofthe following claims is not limited to these embodiments. Variousmodifications, changes, combinations, substitution of equivalents, orthe like can be made within the scope of the following claims.

What is claimed is:
 1. A system, comprising: an actuator; and acontroller configured to drive the actuator with a pulse width modulated(PWM) signal; wherein: the controller is configured to limit a dutycycle of the PWM signal in response to a current supplied by the PWMsignal, a requested duty cycle, and a current limit.
 2. The system ofclaim 1, wherein: the controller is configured to divide a product ofthe current limit and the requested duty cycle by the current suppliedby the PWM signal to generate a duty cycle limit; and the controller isconfigured to limit the duty cycle of the PWM signal in response to theduty cycle limit.
 3. The system of claim 2, wherein the controller isconfigured to limit the duty cycle limit.
 4. A system, comprising: anactuator; a controller configured to drive the actuator with a pulsewidth modulated (PWM) signal; and a power supply configured to supplypower to the controller; wherein the controller is configured to limit aduty cycle of the PWM signal in response to a voltage of the powersupply.
 5. The system of claim 4, wherein the controller is configuredto substantially limit a maximum of the duty cycle of the PWM signal toa ratio of a base voltage to the voltage of the power supply.
 6. Thesystem of claim 5, wherein the base voltage is a rated voltage of theactuator.
 7. The system of claim 6, wherein the rated voltage is lessthan the voltage of the power supply.
 8. A system, comprising: aturbine; an actuator coupled to the turbine and configured to actuate atleast a part of the turbine; an engine coupled to the turbine; and anengine controller coupled to the engine and configured to control anoperation of the engine; wherein: the engine controller is configured todrive the actuator with a pulse width modulated (PWM) signal; and thecontroller is configured to limit a duty cycle of the PWM signal inresponse to a current supplied by the PWM signal.
 9. The system of claim8, further comprising: a cable harness coupled between the enginecontroller and the actuator; wherein the engine controller is configuredto drive the actuator through the cable harness.
 10. A system,comprising: an actuator; and a controller configured to drive theactuator with a pulse width modulated (PWM) signal; wherein: thecontroller is configured to limit a duty cycle of the PWM signal to afirst limit in response to a current supplied by the PWM signal, andsubstantially continuously raise a limit on the duty cycle of the PWMsignal to a second limit.
 11. A method, comprising: driving an actuatorwith a pulse width modulated (PWM) signal; sensing a current associatedwith driving the actuator; combining the sensed current, a currentlimit, and a present duty cycle of the PWM signal to generate a dutycycle limit; and limiting a duty cycle of the PWM signal with the dutycycle limit.
 12. The method of claim 11, further comprising: limiting arequested duty cycle with the duty cycle limit; and driving the actuatorwith a PWM signal having the limited requested duty cycle.
 13. Themethod of claim 11, further comprising limiting the duty cycle limit.